The most common solution is to change their order, so that the most general rule comes last. However, in this case you could use a character class of all characters except a slash, "([^\/]*)", instead of "(.*)".

There might even be a third option. You could modify the index.php to check if there is a slash in the value of $_GET['page'] and if so split it.

FYI, the RewriteCond directives only apply to the first RewriteRule that follows them.